1. Field
Methods and apparatuses consistent with inventive concepts relate to a rotary encoder to detect the rotation angle or revolutions per minute of a rotor, such as a motor or a wheel, and a control method thereof.
2. Description of the Related Art
A rotary encoder, for example, an optical rotary encoder, includes a disc, which is attached to a motor and has a plurality of slits for light transmission, and an optical sensor, which emits light to the plurality of slits and receives the light transmitted through the plurality of slits.
The rotary encoder functions to detect the rotation angle of a motor by observing electric pulse signals produced as the light passes through the plurality of slits. The rotary encoder determines the number of slits having passed through an optical path from a light source based on the number of pulses and, in turn, determines the rotation angle or revolutions per minute of the disc based on the determined number of slits. To ensure accurate determination of the rotation angle or revolutions per minute, the plurality of slits needs to be formed at accurate positions of the disc.
However, conventional processes to manufacture the disc of the rotary encoder have a high probability of forming the plurality of slits at unintentional positions. Moreover, when the disc having the plurality of slits is deformed by the effect of temperature or humidity or other storage problems, positions of the plurality of slits may be distorted.
The distorted positions of the plurality of slits might make it difficult to accurately detect the rotation angle or revolutions per minute of the disc. In other words, if the position of a specific slit provided to represent a specific rotation angle is distorted, the specific slit might actually indicate an unintentional rotation angle that is different from the specific rotation angle. However, since a control unit of the rotary encoder assumes that the specific slit has the specific rotation angle, the assumed angle of the specific slit may differ from the actual angle of the specific slit. This difference might deteriorate reliability in detection of the rotation angle or revolutions per minute of the rotary encoder.
There is need for methods and apparatuses which compensate for and minimize possible positional error of the encoder.